In recent years, compactness, high output, and high voltage tolerance for implementing increases in voltage have been required in rotary electric machines such as electric motors or generators.
In order to make rotary electric machines of this kind more compact, armature windings that have concentrated windings in which conductor wires are wound onto individual armature core teeth have been used with a view to making coil ends, which do not generate effective magnetic flux, more compact. However, compact armatures that use armature windings of distributed winding construction that can suppress torque pulsation and increase output are in demand. In addition, demand for induction machines that do not use magnets has also increased due to steep rises in magnet costs, and there is demand for armatures that use armature windings that have higher-efficiency distributed winding constructions.
Now, in contrast to concentrated windings, which are configured by winding conductor wires onto individual teeth, windings that are configured by winding conductor wires into slots that are separated by two or more slots are called “distributed windings”. In other words, distributed windings are wound such that a conductor wire that extends outward from one slot spans two or more consecutive teeth and enters another slot.
In Patent Literature 1, winding coils that are molded into a helical shape by winding a conductor wire for a plurality of times, also known as “hexagonal coils”, are housed in respective pairs of slots that are separated by a plurality of slots to constitute an armature winding that has a distributed winding construction. Moreover, spacing between the two slots that form the pair of slots is decided based on the number of slots and the number of poles in the armature.
In Patent Literature 2, coil segments that are shaped by bending into a U shape are housed in respective pairs of slots that are separated by a plurality of slots, end portions of the coil segments are bent and folded, and the bent and folded end portions of the coil segments are welded to each other to constitute an armature winding that has a distributed-winding construction.
In Patent Literature 3, a coil assembly that is produced by interweaving a plurality of wave-wound coils in which conductor wires are formed into wave shapes is mounted to a rectangular parallelepiped core, the core in question is rolled up into an annular shape, and butted portions of the rolled-up core are welded to constitute an armature winding that has a distributed-winding construction.